Egg water from the amphibian Bufo arenarum induces capacitation-like changes in homologous spermatozoa

KRAPF, D.; VISCONTI, P.; ARRANZ, SILVIA EDA; CABADA, M.

Developmental Biology

Año: 2007 vol. 306 p. 516 - 524

0012-1606

Mammalian sperm acquire fertilizing capacity after residing in the female tract, where physiological changes named capacitation take place. Inanimals with external fertilization as amphibians, gamete interactions are first established between sperm and molecules of the egg jelly coatreleased into the medium. Since dejellied oocytes are not normally fertilized, the aim of this study was to determine if the jelly coat of the toadBufo arenarum promotes a “capacitating” activity on homologous sperm. We found that sperm incubation in diffusible substances of the jelly coat(egg water) for 90–180 s is sufficient to render sperm transiently capable of fertilizing dejellied oocytes. The fertilizing state was correlated withan increase of protein tyrosine phosphorylation and a decrease of sperm cholesterol content. Inhibition of either the increase in tyrosinephosphorylation or cholesterol efflux affected the acquisition of fertilizing capacity. Phosphorylation and fertilization could be promoted withNaHCO3 and also by addition of beta cyclodextrin. Moreover, sperm could gain the ability to fertilize dejellied oocytes in the presence of thesecompounds. These data indicate that sperm should undergo a series of molecular changes to gain fertilizing capacity; these changes arereminiscent of mammalian sperm capacitation and take place before the acrosome reaction.